Add SimpleSwap swap support

[j0ntz]

CHANGELOG

Does this branch warrant an entry to the CHANGELOG?

• Yes
• No

Dependencies

none

Description

Asana: https://app.asana.com/0/1215088146871429/1217205278669378

Adds SimpleSwap as a centralized swap provider. This is SimpleSwap's own
integration from #481,
recreated on an EdgeApp branch so it can land from here. Their three commits are
preserved with their authorship; the fourth commit is Edge's review pass.

Companion GUI PR: EdgeApp/edge-react-gui#6167.

What the plugin does

src/swap/central/simpleswap.ts calls SimpleSwap API v3 (ranges, estimates,
exchanges) with an x-api-key. It prefers a fixed rate and falls back to a
float rate, checks the pair limits before creating an order, and maps API errors
onto the Edge swap error types. A max quote uses a local fee probe rather than
creating and abandoning a live order. Chain mappings and a mapctl synchronizer
come from SimpleSwap's live currency list, and test/simpleswap.test.ts covers
the mapping for every EdgeCurrencyPluginId plus both quote directions.

Init options: SIMPLESWAP_INIT: { "apiKey": "..." }. The factory throws on an
empty key, so builds without the key skip the plugin.

The Edge review pass (commit 4)

Seven defects. The first four came from driving the plugin against the live API;
the last three came from the reviewer bots on this PR. Each was re-verified
against the live API after the fix:

• Fixed-rate orders to memo and tag chains failed outright. POST /v3/exchanges with fixed: true returns 500 "check extra_id" whenever the
  destination currency carries hasExtraId (XRP, XLM, and every other tag
  chain). Edge pays out to the user's own non-custodial wallet and has no
  destination tag to send, and an empty or null extraIdTo is rejected the same
  way, so the float flow is the only one those pairs can use. The plugin raised
  the 500 as a hard error and never retried, so every swap to those chains
  failed. The retry now covers any fixed-flow failure, not swap errors alone.
• A float-flow server error masked the fixed flow's clean SwapCurrencyError,
  so an unsupported pair surfaced as "SimpleSwap returned error code 500". Both
  errors are ranked now and the more actionable one is thrown.
• denominationToNative results reached the core unrounded. A live ATOM
  quote produced toNativeAmount = 2346482116.51. Minimums round up, maximums
  and receive amounts round down.
• The provider-echoed amountFrom drove the spend with no bound against the
  requested amount. Both directions are bounded now: a from quote requires the
  echoed source amount to equal the amount the order was created from (above it
  overspends, below it underpays a live order), and a reverse quote rejects a
  destination amount below the pinned receive amount.
• A numeric deposit tag was dropped. extraIdFrom cleaned through
  asOptional(asString), so a JSON number tag (XRP, XLM, TON) failed the cleaner
  after the order already existed, and tag 0 was lost. It cleans through
  asNumberString now, and an empty tag is treated as absent rather than
  becoming an empty memo.
• A failure after order creation could open a second order. Everything after
  POST /v3/exchanges returns now runs inside a fatal boundary: the response
  cleaner, the amount arithmetic, the bound checks and the spend construction
  all raise a fatal error that getQuote rethrows instead of retrying. The
  float retry can only run on a failure that happened before the order existed.

Verification

npm run verify passes; the SimpleSwap suite is 26 tests. Driven end to end on
the iOS simulator with every other swap provider disabled locally so the engine
had to route through SimpleSwap: an 80 XLM to XMR swap executed to the success
scene, and the Stellar send carried SimpleSwap's numeric deposit memo.
Screenshots below.

Known gaps, tracked separately

SimpleSwap is receive-only for Zano and Pirate Chain (no sell pair exists in any
direction), and Zcash payouts accept transparent and TEX addresses only, so
there is no unified-address withdrawal. Those are partner-side gaps under
discussion, not plugin defects; the plugin surfaces each as a clean
SwapCurrencyError.

[j0ntz]

📸 Test evidence

simpleswap terms modal

simpleswap quote

swap success

xlm tx with memo

stellar broadcast

Captured by the agent's in-app test run (build-and-test).

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 2 potential issues.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit f3955f2. Configure here.}

[cursor]

Stale comment

Agentic security review of SimpleSwap swap support. One medium finding on partner-returned amounts used for the signed spend without matching the locally pinned quote side.

  

_{Sent by Cursor Security Agent: Security Reviewer}

[cursor]

Agentic security review of SimpleSwap swap support. One remaining medium issue: post-create amount conversion can still throw a non-fatal error and open a second live order.

  

_{Sent by Cursor Security Agent: Security Reviewer}